Water is the single best thing for dehydration, but adding a small amount of salt and sugar speeds up absorption significantly. Your small intestine pulls water into the body faster when sodium and glucose are present together, which is why oral rehydration solutions work better than plain water for anything beyond mild fluid loss. What you drink, what you eat, and how quickly you consume fluids all matter.
Why Salt and Sugar Help More Than Water Alone
Your small intestine has specialized transport proteins that move sodium and glucose into cells simultaneously. When both are present in the right ratio, water follows them through the intestinal wall passively and efficiently. This is the science behind oral rehydration solutions, which the World Health Organization has recommended since the 1970s for treating dehydration worldwide. The current WHO formula, updated in 2003, uses a reduced concentration of sodium and glucose that causes fewer side effects while rehydrating effectively.
You can approximate this at home: mix about six teaspoons of sugar and half a teaspoon of salt into a liter of clean water. It won’t taste great, but it rehydrates faster than water alone. Commercial products like Pedialyte and Drip Drop use the same principle in more palatable formulations. For mild dehydration from exercise or a hot day, plain water with a salty snack achieves a similar effect without the precise mixing.
Best Drinks for Rehydration
Plain water handles most everyday dehydration. If you’ve been sweating heavily, vomiting, or have diarrhea, you need to replace electrolytes too. Here’s how common options compare:
- Water: Sufficient for mild dehydration from not drinking enough during the day.
- Oral rehydration solutions (Pedialyte, Liquid IV): Best for moderate dehydration, illness, or prolonged sweating. They contain the optimal sodium-to-glucose ratio for rapid absorption.
- Sports drinks (Gatorade, Powerade): Contain sodium (about 97 mg per cup) and carbohydrates, making them better than water after intense exercise, though they also contain more sugar than necessary.
- Coconut water: High in potassium (404 mg per cup versus 37 mg in Gatorade) but lower in sodium (64 mg per cup). It’s a solid option for general rehydration but not ideal after heavy sweating, when sodium losses are high.
- Broth or soup: Naturally rich in sodium and easy to consume when you’re feeling ill. Chicken broth is one of the most practical options during stomach illness.
- Milk: Contains sodium, potassium, and natural sugars. Research consistently shows it rehydrates as well as or better than water because the protein and fat slow gastric emptying, giving the body more time to absorb fluid.
Foods That Help With Hydration
About 20% of your daily water intake typically comes from food. Some fruits and vegetables are over 90% water by weight, making them a meaningful source of hydration, especially if drinking large volumes of fluid feels difficult.
The highest-water-content foods include cucumbers and iceberg lettuce (both 96%), celery and radishes (95%), tomatoes and zucchini (94%), and romaine lettuce (94%). Watermelon, strawberries, and cantaloupe are also above 90%. These foods have the added benefit of providing potassium and other minerals you lose through sweat. Eating a bowl of watermelon or a cucumber-heavy salad after time in the heat is a genuinely effective way to rehydrate, not just folk wisdom.
What to Avoid When Dehydrated
Caffeine in moderate amounts (a cup or two of coffee) does not meaningfully worsen dehydration. Research published in Frontiers in Nutrition found that caffeine only triggers significant extra fluid loss at doses around 6 mg per kilogram of body weight, which translates to roughly four or five cups of coffee for an average adult. At half that dose (about two cups), fluid balance stayed normal. So a morning coffee while rehydrating is fine.
Alcohol is a different story. It suppresses a hormone that tells your kidneys to retain water, leading to increased urine output well beyond the volume of fluid you consumed. Beer and wine are less dehydrating than spirits simply because of their higher water content, but none of them help. If you’re already dehydrated, alcohol will make it worse.
Sugary sodas and fruit juices with very high sugar concentrations can also slow rehydration. When the sugar content in your gut is too high relative to the fluid, water actually gets pulled into the intestine rather than absorbed from it, which can worsen diarrhea.
How Much Fluid You Actually Need
The National Academies of Sciences recommends about 15.5 cups (3.7 liters) of total fluid per day for men and 11.5 cups (2.7 liters) for women. That includes water from all sources: drinks, coffee, tea, and food. Most healthy adults meet their needs by drinking when thirsty, but certain situations increase requirements dramatically. Exercise, hot weather, fever, vomiting, and diarrhea can all double or triple your fluid needs for the day.
If you’re actively rehydrating from a noticeable deficit, don’t try to drink it all at once. Sipping small amounts frequently works better than gulping large volumes. Clinical protocols for rehydration typically start with small sips every five minutes, gradually increasing the volume as the body tolerates it. For most adults, steady sipping over one to two hours is enough to resolve mild dehydration.
How to Tell If You’re Dehydrated
Urine color is the simplest self-check. Pale yellow to light straw color means you’re hydrated. Medium yellow suggests mild dehydration. Dark yellow or amber means you need fluids soon. Brown-tinged urine signals severe dehydration. NSW Health uses an eight-point color scale: levels 1 to 2 indicate adequate hydration, 3 to 4 are mildly dehydrated, 5 to 6 are dehydrated, and 7 to 8 are very dehydrated.
Other reliable signs include thirst (obviously), dry mouth, fatigue, dizziness when standing, and headache. In children, look for absence of tears when crying, dry lips, and skin that stays “tented” when gently pinched on the abdomen rather than snapping back immediately. Research from the American Academy of Family Physicians found that a combination of four signs best predicts dehydration in kids: slow capillary refill (press a fingernail and the pink color takes more than two seconds to return), no tears, dry mouth, and generally looking unwell. Two or more of these signs suggest at least 5% fluid loss.
Signs That Need Medical Attention
Most dehydration resolves with oral fluids at home. But severe dehydration is a medical emergency. The red flags include confusion or disorientation, fainting, complete absence of urination, rapid heartbeat, and rapid breathing. These indicate the body can no longer compensate for the fluid loss, and intravenous fluids in a hospital setting are typically necessary. Young children, older adults, and people with chronic illnesses reach this stage faster than healthy adults, so the threshold for concern should be lower in those groups.